Ferreira Tiago J, Vera Ana T, de Moura Beatriz A, Esteves Laura M, Tariq Mohammad, Esperança José M S S, Esteves Isabel A A C
Laboratório Associado para a Química Verde/Rede de Química e Tecnologia (LAQV/REQUIMTE), Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa (FCT NOVA), Costa da Caparica, Portugal.
Front Chem. 2020 Nov 16;8:590191. doi: 10.3389/fchem.2020.590191. eCollection 2020.
Global warming is arguably the biggest scientific challenge of the twenty-first century and its environmental consequences are already noticeable. To mitigate the emissions of greenhouse gases, particularly of CO, there is an urgent need to design materials with improved adsorbent properties. Five different magnetic ionic liquids were impregnated into the metal-organic framework ZIF-8. The composites were produced by a direct-contact method, and their performance as sorbents for gas separation applications was studied. The impact of the ionic liquid anion on the sorption capacity and ideal CO/CH and CO/N selectivities were studied, focusing on understanding the influence of metal atom and ligand on the adsorbent properties. Reproducible methodology, along with rigorous characterization, were established to assess the impact of the ionic liquid on the performance of the composite materials. Results show that the ionic liquid was well-impregnated, and the ZIF-8 structure was maintained after ionic liquid impregnation. The produced composites were of microporous nature and were thermally stable. CO, CH, and N adsorption-desorption isotherms were obtained at 303 K and between 0 and 16 bar. The adsorption-desorption data of the composites were compared with that obtained for original ZIF-8. The general trend in composites is that the increased gas uptake per available pore volume compensates the pore volume loss. Adsorption data per unit mass showed that composites have reversible sorption, but inferior gas uptake at all pressure ranges. This is due to the observed total pore volume loss by the ionic liquid pore occupation/blockage. In most cases, composites showed superior selectivity performance at all pressure range. In particular, the composite [CMIM][MnCl]@ZIF-8 shows a different low-pressure selectivity trend from the original MOF, with a 33% increase in the CO/N selectivity at 1 bar and 19% increase in the CO/CH selectivity at 10 bar. This material shows potential for use in a post-combustion CO capture application that can contribute to greenhouse gas mitigation.
全球变暖可以说是21世纪最大的科学挑战，其环境后果已经很明显。为了减少温室气体排放，尤其是二氧化碳的排放，迫切需要设计具有改进吸附性能的材料。将五种不同的磁性离子液体浸渍到金属有机框架ZIF-8中。通过直接接触法制备复合材料，并研究其作为气体分离应用吸附剂的性能。研究了离子液体阴离子对吸附容量以及理想的CO/CH和CO/N选择性的影响，重点是了解金属原子和配体对吸附性能的影响。建立了可重复的方法以及严格的表征手段，以评估离子液体对复合材料性能的影响。结果表明，离子液体浸渍良好，离子液体浸渍后ZIF-8结构得以保持。所制备的复合材料具有微孔性质且热稳定性良好。在303K和0至16巴之间获得了CO、CH和N的吸附-脱附等温线。将复合材料的吸附-脱附数据与原始ZIF-8的吸附-脱附数据进行了比较。复合材料的总体趋势是，每单位可用孔体积增加的气体吸收量弥补了孔体积的损失。单位质量的吸附数据表明，复合材料具有可逆吸附，但在所有压力范围内气体吸收量均较低。这是由于观察到离子液体占据/堵塞孔隙导致总孔隙体积损失。在大多数情况下，复合材料在所有压力范围内均表现出优异的选择性性能。特别是，复合材料[CMIM][MnCl]@ZIF-8在低压下显示出与原始金属有机框架不同的选择性趋势，在1巴时CO/N选择性提高33%，在10巴时CO/CH选择性提高19%。这种材料显示出在燃烧后二氧化碳捕集应用中的潜力，有助于减少温室气体排放。
